a. Field of the Invention
The instant invention relates to catheters and sheaths and methods of using catheters and sheaths. In particular, the instant invention relates to steerable catheter or sheath control handles and methods of manufacturing and using such handles.
b. Background Art
Catheters that have flexible tubular bodies with deflectable distal ends and control handles for controlling distal end deflection are used for many noninvasive medical procedures. For example, catheters having conductive electrodes along the distal ends of their bodies are commonly used for intra-cardiac electrophysiology studies. The distal portion of such a catheter is typically placed into the heart to monitor and/or record the intra-cardiac electrical signals during electrophysiology studies or during intra-cardiac mapping. The orientation or configuration of the catheter distal end is controlled via an actuator located on a handle outside of the body, and the electrodes conduct cardiac electrical signals to appropriate monitoring and recording devices that are operatively connected at the handle of the catheter.
Typically, these catheters include a generally cylindrical electrically nonconductive body. The main body includes a flexible tube constructed from polyurethane, nylon or other electrically non-conductive flexible material. The main body further includes braided steel wires or other non-metallic fibers in its wall as reinforcing elements. Each electrode has a relatively fine electrically conductive wire attached thereto and extending through the main body of the catheter. The conductive wire extends from the distal end to a proximal end where electrical connectors such as plugs or jacks are provided to be plugged into a corresponding socket provided in a recording or monitoring device.
The distal portion of the main body is selectively deformed into a variety of curved configurations using the actuator. The actuator is commonly internally linked to the distal portion of the catheter by at least one actuation wire. Some catheters employ a single actuation wire, which is pulled (i.e., placed in tension) by the actuator in order to cause the distal portion of the main body to deform. Other catheters have at least two actuation wires, where the actuation of one wire (i.e., placing one wire in tension) results in the other wire going slack (i.e., the wire does not carry a compressive load). In such catheters, where the actuation wires are not adapted to carry compressive loads (i.e., the actuation wires are only meant to be placed in tension), the actuation wires are commonly called pull or tension wires.
To deform the distal end of the catheter into a variety of configurations, a more recent catheter design employs a pair of actuation wires that are adapted such that one of the actuation wires carries a compressive force when the other actuation wire carries a tensile force. In such catheters, where the actuation wires are adapted to carry both compressive and tension loads, the actuation wires are commonly called push/pull or tension/compression wires and the corresponding catheter actuators are called push-pull actuators. U.S. Pat. No. 5,861,024 to Rashidi, which issued Jan. 19, 1999, is representative of a push-pull actuator of this type, and the details thereof are incorporated herein by reference.
While many of the existing catheter actuators provide precise operation and good flexibility in movement of the distal portion of the body, the existing actuators often offer a range of distal portion displacement that is less than desirable. In other words, the amount of push/pull of the actuation wires (i.e., the steering travel) is often inadequate for the medical procedure being performed. The inadequacy of the steering travel typically results from the generally limited size of the actuator body, which is usually sized for receipt and manipulation between the thumb and index finger of a user's hand. Accordingly, a need exists to provide an improved actuating assembly for a catheter that increases the amount of steering travel associated with the actuator.
Similarly, once the distal portion has reached a desired position, the physician must either hold the catheter and the actuator in position to keep the distal portion in the desired position, or the handle of the catheter requires the physician to take a conscious step to maintain the distal portion of the catheter at the desired position. Accordingly, a need exists to provide an improved catheter and actuating assembly for a catheter that automatically holds the distal end of the catheter in the desired position. There is also a need in the art for a method of manufacturing and using such a catheter.